Need advice what to do with axle

As some of you might know, I purchased the GS455 clone convertible which Wallypep did create some years ago. Now that the car finally arrived in Germany I had the opportunity to take it couple of times for a ride. Boy, that engine has so much punch, that it is hard to avoid to spin tyres. According to Wally the axle is stock (1970 350 2bbl). I was not able to read any identification on the axle. Per my research it is a 8.2 non posi 2.56 unit. Even though I am not planning to do quarter mile stuff I would like to upgrade the axle with a posi-unit. And here comes the trouble: It looks like the choices are somewhat limited as this is the 8.2 Buick only axle. The Posi-units I found online will not work with 2.56 ratio. I am hesitant to go higher with the ratio because
1. as I stated already I do not want to become the 1/4 mile champion
2. driving in Germany takes one frequently in the speed range of 70-80 miles/hour and I do not want the engine reving that high while cruisin

Ralf, Well that 1968-1970 era stock 10 bolt 8.25 rear does not really have any aftermarket options that are not CUSTOM.
I can make you a 2.56 posi will take some doing but we have done a couple before yours. 2.73 or 2.93 are easier. BUT IT CAN BE DONE... Just PM me your email and we can work on it for you. Jim
J D Race

I made up my mind, as I dicided to go to an OD-trans. Also, I will stick with my buick only axle. I will not stick with the 2.56 which is installed right now. I am leaning towards 3.23 or 3.42 with a posi. Do I have more options with the new ratios, I am leaning towards?

With OD you want the 3.42 at least. I had 3.31 and 3.55 in my ss 454 Monte Carlo and 3.31 for sure when passing was doggie on the freeway. 3.55 was not bad if you do alot of state to state shows. 3.64 is a great ratio if you r hanging more with in 200-300 mile rane for show and like the track some too.